foo.ts

//action
export const loginAsync = createAsyncAction(
  'LOGIN_REQUEST',
  'LOGIN_SUCCESS',
  'LOGIN_FAILURE'
)<undefined, Auth, string>()


//reducer
const loginReducer = createReducer(initialState as Auth)
  .handleAction(loginAsync.request, (state) => {
    return ({ ...state, loading: true })
  })

//rootSaga
  takeEvery(getType(actions.auth.loginAsync.request), authenticate)
  
// saga (authenticate function)
 export function* authenticate (action: Action): Generator {
  yield put(loginAsync.success({
    foo: 'Bar'
  }))
}